The present invention relates to a cosmetic comprising a neutral polysaccharide obtained from acid-fast bacterium.
A polysaccharide is an important biopolymer as well as a nucleic acid, a protein and a lipid, and is utilized in pharmaceutical, food and agricultural chemicals industries and the like. In the field of cosmetics, various polysaccharides have been used as water-soluble highmolecules exerting excellent moisture-retaining or thickening effect. The polysaccharides heretofore used for comsmetics include acidic polysaccharides such as alginic acid, pectin, chondroitin sulfate and hyaluronic acid and neutral polysaccharides such as cellulose, starch, dextran and pullulan. The acidic polysaccharides are defective in that because of ionic characteristic thereof, applicable surfactants are limited and the viscosity is greatly changed with changes in the pH value. The above neutral polysaccharides from natural extracts are defective in that since they ordinarily have a high molecular weight and the distribution range of the molecular weights is wide, the viscosity is high and they do not always give a good feeling during or after use when they are incorporated in cosmetics. Furthermore, neutral polysaccharides become tacky during use or leave a pasty touch after use.
Under the above-mentioned circumstances, the inventor made research with a view to eliminating the above defects and found that a neutral polysaccharide obtained from an acid-fast bacterium has a high water solubilitiy and can exhibit a good moisture-retaining effect to the skin and that its molecular weight is relatively low and the molecular weight distribution range is narrow so that an aqueous solution of this neutral polysaccharide has a low viscosity and can be easily incorporated into a cosmetic base without any great change of the liquid property. It also was found that since this neutral polysaccharide was non-ionic, surfactants could be freely selected and the emulsion stability was good, and that the viscosity were not changed with changes in the pH value. In short, it was found that this neutral polysaccharide has various excellent properties as a cosmetic additive. We have now completed the present invention based on these findings.